Declaring it's never too late to make things right, President Barack Obama posthumously bestowed the Medal of Honor on two World War I veterans whose heroic acts nearly 100 years ago went unrecognized in an age of discrimination.

In a tearful, joyful East Room ceremony recalling the battlefield triumphs as well as the prejudices of 20th century America, Sgt. William Shemin and Pvt. Henry Johnson were recognized with the nation's highest military decoration for saving their comrades on French front lines. Shemin was Jewish and Johnson was black.

"It has taken a long time for Henry Johnson and William Shemin to receive the recognition they deserve, and there are surely others whose heroism is still unacknowledged and uncelebrated," Obama said.

'We are forever grateful'

"The least we can do is to say we know who you are, we know what you did for us, we are forever grateful," he said.

Obama applauded the tireless efforts of their advocates, who led Congress to pass an exemption from Medal of Honor rules specifying that heroic actions have to have taken place within five years to be considered.

President Barack Obama posthumously bestows the Medal Of Honor for Army Sgt. William Shemin to his daughters Ina Bass, left, and Elsie Shemin-Roth, of suburban St. Louis, in the East Room of the White House in Washington, June 2, 2015.

Shemin's daughters were full of emotion as Obama handed them the star-shaped medal hanging from a blue silk ribbon that they felt was long denied their father because of anti-Semitism. Ina Bass, 83, thrust the audience a thumbs up and planted a kiss on the president's cheek, while 86-year-old Elsie Shemin-Roth smiled through her tears.

Veterans of Johnson's New York National Guard regiment, the 369th known as "Harlem Hellfighters," watched stoically as Obama described how he died destitute in his early 30s after his injuries left him crippled and unable to work.

"America can't change what happened to Henry Johnson," Obama said. "We can't change what happened to too many soldiers like him, who went uncelebrated because our nation judged them by the color of their skin and not the content of their character. But we can do our best to make it right."

Obama described how Johnson and a fellow soldier came under attack by at least a dozen German soldiers while on night sentry duty on May 15, 1918. Both were injured, but Johnson single-handedly beat back the invading party and rescued his unconscious brother in arms, armed with just his Bolo knife after his rifle jammed.

Obama said Johnson became famous -- feted at a victory parade down Fifth Avenue, his picture printed on recruitment posters and President Teddy Roosevelt writing that he was one of the bravest men in the war.

WATCH: Medal of Honor ceremony

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The French, who commanded his unit because U.S. armed forces were segregated at the time, gave him the country's highest award for valor. A statue of Johnson is displayed in his hometown of Albany, N.Y.

"But his own nation didn't award him anything, not even the Purple Heart, though he had been wounded 21 times. Nothing for his bravery, though he had saved a fellow soldier at great risk to himself," Obama said before presenting the award to New York National Guard Command Sgt. Maj. Louis Wilson.

Honor took too long

Obama said it similarly took too long for America to properly honor Shemin, who was 19 when his platoon was involved in a bloody fight on the western front beginning Aug. 7, 1918. Obama said over the course of three days, Shemin repeatedly raced through heavy machine gun fire to rescue fallen comrades.

"Eventually, the platoon's leadership broke down. Too many officers had become casualties. So William stepped up and took command," Obama said.

A German bullet pierced his helmet and lodged behind his left ear. Shemin was hospitalized for three months and was left partly deaf. Shrapnel wounds eventually left him barely able to walk, although he earned a degree from Syracuse University and ran a nursery business in the Bronx before his death in 1973.

"Sergeant Shemin served at a time when the contributions in heroism of Jewish Americans in uniform were too often overlooked," Obama said. "But William Shemin saved American lives. He represented our nation with honor. And so it is my privilege on behalf of the American people to make this right."